Philly's sidewalks and the fickle space between public and private

Legally, sidewalk repair is the responsibility of homeowners, but historically, enforcement of upkeep has been thin. [...]

“[sidewalks] should be part of the money we spend on transportation ... because people who walk are transporting themselves on their feet.” [...]

The liability is actually two-tiered: The property owner is responsible if someone sues after an injury due to poorly maintained sidewalks, but the city has secondary responsibility because sidewalks are public infrastructure.
— nextcity.org